This invention generally pertains to nozzles for injection molding. More specifically, the present invention relates to a nozzle for the fluid-assisted injection molding of plastic materials.
Such nozzles are illustrated in U.S. Pat. Nos. 4,905,901 dated Mar. 6, 1990; 5,151,278 dated Sep. 29, 1992 and 5,164,200 dated Nov. 17, 1992. These three patents are owned by the assignee of the instant application. The disclosures of these three patents are incorporated herein by reference in their entireties.
Several recently perfected nozzles do away with many of the disadvantages of employing gas assisted injection molding. In these nozzles, a pin is located in a longitudinally extending bore of a barrel of the nozzle. In the embodiment disclosed in the U.S. Pat. No. 5,151,278, the pin remains stationary as the barrel of the nozzle reciprocates in relation to the pin. In the embodiments disclosed in the U.S. Pat. No. 5,164,200 and the U.S. Pat. No. 4,905,901, the pin and the barrel reciprocate together since the pin is operatively secured to the barrel. In each of these designs, however, a relatively long pin is employed which may be on the order of 15 inches. Such a pin is difficult and expensive to manufacture. In addition, a barrel with such a long pin in the barrel bore is difficult to clean and maintain should it become necessary to remove plastic material which may have flowed into the annular passage formed between the pin and the inner periphery of the barrel, around the bore.
Accordingly, it has been considered desirable to develop a new and improved gas assisted injection molding nozzle which would overcome the foregoing difficulties and others while providing better and more advantageous overall results.